Safety belt restraint devices, particularly those with inertia-sensitive locking means, have been known in the art for several years. There is constant development within this industry to produce improved devices which will restrain a passenger in an emergency with an economy of moving parts and at minimal costs while having these passenger restraint devices operate with a minimal interference with the occupant in order to promote more frequent use of the restraint devices.
Many safety belt systems which are known in the art utilize a spring-biased reel mounted within a retractor mechanism about which is wound a protractable length of seat belt webbing material. In one class of these restraint devices, the occupant may freely cause protraction and retraction of the seat belt as the occupant moves within the vehicle seat during normal conditions in a relatively unconfined manner. During emergency conditions, these retractor mechanisms are provided with an inertia sensor for sensing the emergency condition and prevent further protraction of the seat belt once the emergency condition is encountered thereby restraining the occupant for the duration of the emergency.
One such retraction device incorporates as a main feature a pawl and ratchet-wheel construction for locking the spool or reel about which the safety belt is wound against further protractive rotation. As disclosed in U.S. Pat. No. 3,918,658 issued to Herbert R. Beller on Nov. 11, 1975 and entitled "Seat Belt Retractor Having Inertial Device Activated by Two Stimuli", a retractor mechanism is disclosed which includes a retractor spool about which a seat belt webbing is wound, a first inertia sensor which comprises a pendulum which is responsive to the inertia of the vehicle, a second inertia sensor which is responsive to excessively rapid protractive rotation of the spool, and a pawl which, in this case, is responsive to both of the inertia sensing devices to cause engagement with the ratchet teeth of the spool and thereby prevent further protractive rotation of the spool.
One of the disadvantages of spool locking retractor devices is that even though the reel or spool itself becomes locked during an emergency condition, a certain amount of protraction of the safety belt can still occur depending on the manner in which the belt is wound about the reel and its relative compactness. In other words, the belt may slide along itself further compacting the layers wound on the reel providing an additional amount of slack to the belt.
In a co-pending application, Ser. No. 227,275 filed Jan. 22, 1981 by Avraham Ziv and entitled "Safety Belt Webbing Emergency Locking Apparatus", assigned to the common assignee of this invention and incorporated herein by reference, an improvement to such devices was disclosed by providing a single clamping wedge disposed at a location between the retractor reel and the vehicle occupant and having the safety belt passing therethrough. In the apparatus of that invention, in addition to the inertia-responsive device for causing lock-up of the retractor reel itself, a second inertia responsive device was provided for activating the clamping wedge which more directly clamped the safety belt preventing any further protraction whenever the second inertia sensor encountered a level of inertia greater than that necessary to cause lockup of the reel-associated sensor. In this manner, in more severe emergencies, an immediate and more reliable lock-up of the belt was accomplished.
In a subsequent co-pending application, Ser. No. 343,896 filed Jan. 29, 1982, by Avraham Ziv and entitled "Protractive Force Responsive Safety Belt Locking Apparatus", assigned to the common assignee of this invention and incorporated herein by reference, it was further identified that in a dual locking retractor such as the one just described, after a primary lock-up of the retractor spool and before the greater threshold vehicle inertia was encountered to trigger the belt clamping wedge, differing amounts of slack would play out of the locked reel of wound webbing material depending upon the weight of the occupant. This weight or force responsive protraction would vary independent of the degree of vehicle inertia encountered in the emergency condition and thus a non-uniform degree of restraint is provided by the previous apparatus. In the apparatus of the subsequent invention, the clamping wedge is responsive to that weight or force which the individual imparts to the seat belt during the emergency condition thereby causing immediate and assured lock-up of the safety belt webbing. Locking of the webbing would thus occur in response to forces exerted on that webbing such as during a slow-developing emergency condition where the greater vehicle threshold inertia of the previous-described invention would not be achieved. More specifically, in the apparatus of the later invention, a pendulum-type inertia sensor senses a first level of vehicle inertia associated with an emergency condition and causes lock-up of the spool in the conventional manner. Further forces on the vehicle occupant associated with the emergency condition causes the safety belt to be tensioned such that protractive slipping of the winds of webbing about the locked spool might cause further protraction or slackening of the belt. Forces associated with this further protraction are transmitted to the spool which is mounted in a retractor assembly which is slideably attached to the retractor frame and biased toward an unlocked position. The increasing force upon the safety belt which would otherwise cause further belt slippage and protraction, instead causes the retractor simply to slide relative to the frame and this sliding, in turn, activates a clamping wedge similar to that previously described thereby causing an immediate and an assured clamping of the safety belt and preventing further protraction even though the windings of the belt around the reel have not achieved full compactness and further slippage would have been possible.
While the apparatus of the last-described invention is well suited for its purpose, the use of a sliding mounting apparatus for the retractor reel requires a significant number of moving parts, is costly to manufacture and assemble, and required movement of the retractor. Wherefore, it is an object of the present invention to provide an alternative embodiment to the invention of the aforementioned application which alternate embodiment is similarly responsive to protraction forces on the seat belt webbing itself following primary lock-up of the reel but which eliminates the requirement of a sliding construction and adds a geometry and design affording economical manufacture.
It is a further object of the present invention to adapt the alternative embodiment to utilize and adapt a feature found for example in FIG. 3 of U.S. No. 3,834,646 filed Sept. 10, 1974 by Robert B. Heath and entitled "Take-Up Spool Latch". In the apparatus of that invention, first and second sets of pawls and ratchet wheels are utilized in association with a pendulum-type inertia sensor and locking ratchet wheel to prevent a false-locking condition. A condition in which the primary pawl and ratchet wheel engage in a tip-to-tip relationship or a premature release of lock-up occurs. The apparatus of that invention provides a second programming pawl and ratchet assembly formed of deformable plastic material which guides the engagement of the primary pawl and ratchet wheel into a meshed lock-up assured relationship. Therefore, it is a further object of the present invention to adapt the teachings of that patent into the aforementioned alternative embodiment, particularly since the integrated dual locking feature of the locking reel plus the clamping wedge or weblocker in this alternative embodiment are to be responsive to a single vehicle inertia sensor or pendulum mass.